CN102405434A - Improvements in methods for producing lens arrays - Google Patents

Abstract

There is provided a lens array for imaging a plurality of image elements in an object plane, and a method of making a lens array. The lens array includes a plurality of lenslets formed in or on one side of a transparent or translucent material with the image elements disposed on the opposite side, and has a gauge thickness corresponding to the distance from the apex of each lenslet to the object plane. Each lenslet has a set of lens parameters. The gauge thickness and/or at least one lens parameter is or are optimised such that each lenslet has a focal point size in the object plane which is either substantially equal to the size of the image elements in the object plane, or varies from the size of the image elements by a predetermined amount.

Description

Improvement to the method for producing lens arra

Technical field

The present invention relates to be used to design and make the improved method of lens arra, and relate to the lens arra of producing thus.

Background technology

Lens arra allows to produce the optical effect of number of different types.For example; The lens arra that focuses on a plurality of base map elements of locating its focal plane can produce the general image that looks like three-dimensional; This image moves, changes magnification or distortion along with the variation at visual angle, perhaps this image has the apparent degree of depth outside the plane of this lens arra.Can realize further effect through two or more images are interweaved at (for example in the striped under a plurality of cylindrical lens) under the lens, make that like this beholder sees pictures different with visual angle change.This type of visual effect is useful in multiple application (comprising display, targeted promotional material, collectibles) and as the optically variable device in the secure file.

Lens arra is generally processed by transparent polymer material, so that produce a material sheet, is referred to herein as lenticular sheet.The pattern that forms these lenslets of this array is on an embossing or the side that otherwise is formed on thin slice, and the opposite side of thin slice is formed smooth, a smooth surface generally.These pictorial elements are applied in or place on this even curface and can for example perhaps form through laser labelling technology through printing.This sheeting is normally made as an individual layer, but also can use multilevel method.

Pictorial element can comprise a plurality of printing points.In a kind of technology, before printing, a continuous images representing desirable final printed article on this flat surface is converted into a kind of half tone image.After the printing, this half tone image will be revealed as a plurality of printing points on this flat surface.

The thickness of lenticular sheet (being commonly called gauge thickness) has been determined by the focal length of these lenslets routinely, makes the light of incident focus on the flat surface place of thin slice basically like this.Select this design to utilize so-called sampling effect.The sampling effect has been guaranteed to be printed on of focal length of lens place and is named a person for a particular job and manifest to the observer as a line that strides across right cylinder lens at a certain viewing angles place, and appears to for non-cylindrical lens and filled whole lens area.Therefore, the observer can't distinguish two inner adjacent points of a single lens at a specific place, visual angle.

In some cases, can be according to the material thickness and the lens frequency (or spacing) that the metering limit of the needs of final products and sheeting manufacturing process is selected in advance these lenslets.Then, confirm the radius-of-curvature of these lens based on extra parameter (like the refractive index and the Abbe number of used polymeric material), so that the light of incident is focused on the burnishing surface of thin slice basically.

The nearest trend in this area is to be to produce thinner lenticular sheet so that reduce manufacturing cost, the potential application of meanwhile widening the optical effect object always.Yet thinner lenticular sheet requires higher lens frequency generally, so that produce focusedimage.For example, the material with 85 microns gauge thickness production will require the approximately lens frequency of every centimetre of 224 lenslets in polyester.The imaging of printing optical effect is challenging especially on the microlens array of these frequent, and has seriously limited the type of the effect that can realize and the type of operable compacting and preloading method.In addition, often cause high scrap rate because must use the silk screen of very high line number, and make point-device color become most important the contraposition of color.These problems have meaned uses very that the lenticular sheet material of frequent so far is restricted.

At U.S. Patent number 6,833, a kind of trial that overcomes the problems referred to above has been described in 960.In printing machine, on a kind of substrate that uses curable resin, a plurality of lens shaped are become a plurality of hemisphere.In this method, on-chip these lens are formed on their focus.Therefore, these lens are out of focus basically, and this makes that the sampling effect is invalid.Therefore the image that is produced by this method blurs basically.

At U.S. Patent number 6; 989; Another kind of method has been described in 931; It comprises a kind of combination picture, and this image comprises and sees through a lens screen from one first many printing stripeds that angle is visible, is visible and place object or the image of a distance of this lens screen face behind the scenes to see through a plurality of transparent stripeds one second angle.In one embodiment, considered a kind of lens material thinner than its focal length.Yet a random out of focus design with this character is inapplicable for multiplexing lens imaging or complicated Moire effect, because it possibly produce serious fuzzy and loss picture contrast.

Correspondingly, for a kind of do not introduce substantial fuzzy or other can be offensive the situation of image artifacts under reduce the gauge thickness of lens arra method exist needs.

What in some cases, possibly make us hoping is to make lenticular sheet with a specific gauge thickness.If this situation, what possibly hope so is to reduce the lens frequency, promptly increases the width of each lenslet, so that guarantee picture quality in view of the restriction that typography to be used (or be used to form other technologies of the pictorial element) is arranged.Therefore that makes us hoping provides a kind of lens arra and a kind of method, and this method allows under the situation of not introducing substantial fuzzy or other offensive image artifacts, to use lower lens frequency.

Comprised that any discussion to document, effect, material, device, object or the like in this manual all is only to be used to the present invention a background is provided.This must not be considered to admit in these materials any or whole part that forms the prior art basis, or before the priority date of each item claim of the application, just be present in the public general knowledge in the Australian field relevant with the present invention as it.

Summary of the invention

In one aspect; The invention provides a kind of being used at the lens arra of objective plane with a plurality of pictorial element imagings; This lens arra comprise be formed on a kind of transparent or semitransparent material one side among or on a plurality of lenslets; And these pictorial elements place on the opposition side; This lens arra have with from the summit of each lenslet to the corresponding gauge thickness of the distance of this objective plane; Wherein each lenslet has one group of lens parameter, and this gauge thickness and/or at least one lens parameter are optimised for and make each lenslet in this objective plane, have a focal spot size, and this focal spot size equates basically with the size of these pictorial elements in this objective plane or differs predetermined value with the size of these pictorial elements.

In another aspect of the present invention; Provide a kind of manufacturing to be used at this in the method for objective plane with the lens arra of a plurality of pictorial element imagings; This lens arra comprises a plurality of lenslets; This lens arra have with from the summit of each lenslet to the corresponding gauge thickness of the distance of this objective plane, this method may further comprise the steps:

Confirm a scale parameter, the size of this parameter representative these pictorial elements at least a portion of this objective plane;

For each lenslet, use this scale parameter to optimize at least one parameter in this gauge thickness and/or the one group of lens parameter;

And with said gauge thickness and said lens parameter within a kind of transparent or semitransparent material one side or on form this lens arra, wherein these pictorial elements are placed on the opposition side of this transparent or semitransparent material;

Thus, make these lenslets in this objective plane, have a focal spot size, this focal spot size equates basically with the size of these pictorial elements in this objective plane or differs a predetermined value with the size of these pictorial elements.

This group lens parameter can comprise lens width, refractive index, sag (sag) highly, radius-of-curvature, circular cone parameter and Abbe number.Can change a part of or whole of these parameters so that in objective plane, obtain to have a focal spot size of desirable characteristic.

Preferably, each lenslet has the cross section of conic section.These lenslets can be columniform or have a spherical or aspheric cross section of part.Each lenslet is preferably rotational symmetric in the plane of this lens arra.In one embodiment, each lenslet can be long and narrow microtrabeculae lens, and it has along the uniform basically cross section of its length.

Definition

Focal spot size H

As employed at this, term " focal spot size " is meant under a certain viewing angles yardstick of the geometric distributions of these points that light and the objective plane through a lens refraction is crossing, normally effective diameter or width.This focal spot size can be inferred from the simulation of Theoretical Calculation, ray tracing or from actual measurement.Ladies and gentlemen inventor has been found that the software that uses like ZEMAX carries out the ray tracing simulation and the direct measured value according to the lens that method described here designed is mated very much.Ray tracing simulation can be adjusted so that be not that exactly parallel situation is taken into account with incident ray in the reality.

Focal distance f

In this manual; When using with reference to the lenticule in the lens arra; Focal length is meant the distance from lenticular peak to focal position; This focal position is (referring to the T.Miyashita, " Standardization for microlenses and microlens arrays " (2007) Japanese Journal of Applied Physics 46, p 5391) through confirming when collimated light that the peaked position of power density distribution provides during from the lens side incident of array.

The gauge thickness t

Gauge thickness is from the distance on the surface to the opposition side of this trnaslucent materials on the summit of a lenslet on a kind of side of transparent or semitransparent material, on the surface of this opposition side, is equipped with the pictorial element that overlaps with objective plane basically.

Lens frequency and spacing

The lens frequency of lens arra is at a number to the lenslet on the set a distance that strides across this lens arra surface.Spacing is to the distance on the summit of adjacent lenslet from the summit of a lenslet.In a uniform lens arra, spacing and the lens frequency relation of being inversely proportional to.

Lens width W

The width of the lenslet in the microlens array is to the distance of the opposite edge of this lenslet from an edge of this lenslet.In the lens arra with semisphere or half-cylindrical lenslet, this width will equal the diameter of lenslet.

Radius of curvature R

The radius-of-curvature of lenslet be from a point on the lens surface to the normal of this lens surface with vertically passing the line (lens axis) that extends on the lenslet summit distance of a crossing point.

Sag height s

The sag of lenslet height (sag height) or surperficial sag s are the distances between the crossing point of the short lines that passes that axis normal extends from summit to this axis and edge from lenslet.

Refractive index n

A kind of refractive index n of medium is a light speed in a vacuum and the ratio of the speed of light in this medium.The refractive index n of lens has confirmed that light reaches the amount that lens surface will be reflected, according to snell law:

n ₁*Sin(α)＝n*Sin(θ)，

Wherein α is the angle of normal at the incidence point place of incident ray and lens surface, and θ is the angle of the normal at refracted ray and incidence point place, and n ₁Be the refractive index (n of air ₁Can get 1 approx).

Constant of the cone P

Constant of the cone P is an amount describing conic section, and is used in the geometrical optics to specify circular (P=1), oval-shaped (0＜P＜1 or P＞1), parabolical (P=0) and hyp (P＜0) lens.Some list of references is represented the constant of the cone with alphabetical K.K interrelates through following formula and P: K=P-1.

The lobe subtended angle

The lobe subtended angle of lens is the whole visual angles that formed by these lens.

Abbe number

A kind of Abbe number of transparent or semitransparent material is the tolerance to material dispersion (refractive index is with wavelength change).The Abbe number of lens is carried out suitable choice can help aberration is minimized.

Secure file

As employed at this; Term " secure file " comprises value documents and the mark and the identification document of all kinds, includes but not limited to following: currency object such as currency and coins, credit card, check, passport, I.D., security and share certificate, driving license, ownership certificate, travel document such as aircraft and train ticket, gate inhibition's card and admission ticket, births & deaths and marriage certificate and academic record are single.

Transparent window and half window

As employed at this, term " window " is meant a transparent or semitransparent zone of in secure file, comparing with the opaque zone that applies printing basically.This window can be fully transparent, makes it allow optical transmission unaffected basically like this, and perhaps it can be a partially transparent or translucent, thereby partly allows optical transmission but do not allow clearly to see object through window area.

Window area can be in a kind of polymkeric substance secure file, to form through in the scope that forms window area, removing at least one light non-transmittable layers, and this secure file has one deck transparent polymer material at least and is applied to the one or more light non-transmittable layers at least one side of transparent polymer substrate.If light non-transmittable layers is applied on the both sides of transparent substrate, can form a complete transparent window through the light non-transmittable layers of in window area, removing the transparent substrate both sides so.

A partially transparent or translucent zone (below be referred to as " half window ") can form through the light non-transmittable layers of in window area, only removing secure file one side in a kind of both sides all have the polymkeric substance secure file of light non-transmittable layers, make " half window " not to be transparent fully but to allow a part of light to pass but do not allow to come clearly to watch object through half window like this.

Alternately; Might form substrate from a kind of opaque basically material (like paper or fibrous material), one of them transparent plastic material embolus is inserted in excision portion or the depression in paper or the fiber substrate so that form a transparent window or a translucent half window zone.

Light non-transmittable layers

Can one or more light non-transmittable layers be applied on the transparent substrate to increase the opacity of secure file.Light non-transmittable layers is for making L _T＜L ₀, L wherein ₀Be the amount that incides the light on the file, and L _TIt is the amount that the light of file is passed through in transmission.Light non-transmittable layers can comprise any or multiple in the multiple light tight coating.For example, light tight coating can comprise and is dispersed in pigment a kind of thermal activation, within crosslinkable polymeric material bond or the carrier, like titania.Alternately, can a kind of transparent plastic material substrate be clipped in paper material or other partially or substantially between a plurality of light non-transmittable layers of opaque material, subsequently can on it, print or otherwise apply indicant.

In one embodiment of the invention, the gauge thickness of lens arra can be that size and lens parameter group with respect to these pictorial elements is optimized.

In another embodiment, lens parameter can be that size and gauge thickness with respect to these pictorial elements is optimized.

Through selecting lens parameter to make focal spot size relevant, can reduce the thickness or the lens frequency of lens arra, and can not sacrifice picture quality basically with the size of pictorial element.This is because will still with under desirable one or more visual angles be intersected by a pictorial element region covered through lenslet refraction and most of light of reaching objective plane, and this just allows to guarantee the sampling effect.

The thickness of lens arra can be reduced the lenticular sheet that more approaches to provide, but it still can bring high-quality image effect.Alternately, can when guaranteeing thickness, these lenslets be widened,, therefore improve picture quality and/or allowed to produce more complicated visual effect so that allow under each lenslet, to comprise more printing.

Preferably, the thickness of lens arra is less than the focal length of all these lenslets.

In an especially preferred embodiment, the predetermined value that differs of focal spot size and pictorial element size is less than the difference value of an estimation of pictorial element size.The difference value of this estimation can be standard deviation, mean absolute deviation or the range interquartile (interquartile range) of these pictorial element sizes.If focal spot size is greater than the size of pictorial element; This keeps desirable picture quality basically when allowing a kind of even thinner lenticular sheet so; Because in general, the sub-fraction power density distribution of having only refracted ray is in the edge of this hot spot.If focal spot size is smaller, can make the transition between the image component that produces image effect more level and smooth so.

In practice, we have found that one predetermined according to variation and fixed value up to 20% can still be taken the variation of printed pictorial element size in most cases into account when producing high-quality imaging.Yet if require higher degree of accuracy, this difference value can be distributed by the physical size of printed pictorial element through above-mentioned any method and estimate.

These pictorial elements can be taked the form of point, line or other shapes.Can these pictorial elements be applied on the surface in the objective plane on the opposition side of this transparent or semitransparent material by many modes (comprising laser labelling).In a preferred embodiment, pictorial element is to be printed on the said surface of objective plane.Method of the present invention can may further comprise the steps: a plurality of printing points are applied on surface behind of the transparent or semitransparent material that is formed with a plurality of lenslets on the front surface, so that form a kind of device or object of optically-variable.Alternately, can a plurality of printing points be applied on (for example fiber or polymeric material) substrate, and this substrate is attached on the back surface of this transparent or semitransparent material.

These lenslets can be formed by embossing technique in a kind of material of transparent or semitransparent radiation-hardenable.The material of this transparent or semitransparent radiation-hardenable can be cured after embossing, but preferably side by side carries out embossing and curing basically.Substrate preferably forms from a kind of transparent or semitransparent polymeric material, and wherein the material of substrate and radiation-hardenable combines the gauge thickness of thickness corresponding to lens arra.In an especially preferred embodiment, this substrate is the structure of a kind of flexibility, similar thin slice, and the material of substrate and radiation-hardenable has formed the part of secure file (like bank note, credit card or the like).This substrate preferably has the refractive index substantially the same with these lenslets.

In a preferred embodiment, the lens parameter group is identical for each lenslet.

In another preferred embodiment; After averaging on the both direction at least in the lobe subtended angle at lenslet; Focal spot size is the size that is substantially equal to these pictorial elements, and perhaps the size with these pictorial elements differs a predetermined value.

These directions that focal spot size averages above that are preferably incorporated near axle (on-axis) direction and the lobe subtended angle edge one from axle (off-axis) direction.

In yet another aspect; The invention provides one of design is used in the method for objective plane with the lens arra of a plurality of pictorial element imagings; This lens arra comprise a plurality of lenslets and have and from the summit of each lenslet to the corresponding gauge thickness of the distance of this objective plane, this method may further comprise the steps:

Estimate a scale parameter, the size of this parameter representative these pictorial elements in this objective plane,

For each lenslet is selected one group of lens parameter, and

Use this scale parameter to design this lens arra so that optimize at least one lens parameter of the lens parameter group of this gauge thickness and/or each lenslet; Wherein each lenslet has a focal spot size in this objective plane, and this focal spot size equates basically with the size of these pictorial elements in this objective plane or differs a predetermined value with the size of these pictorial elements.

Preferably, the thickness of a lens arra that comprises these lenslets is less than the focal length of all these lenslets.

The lens parameter group can be identical for each lenslet.Alternately, these lenslets in one or more zones of lens arra can have and the different lens parameter of lenslet at the remainder of lens arra.

Preferably, this method further may further comprise the steps: at least a portion of this objective plane, measure the size of these pictorial elements, wherein this scale parameter is to estimate from the measured size of these pictorial elements.This measurement can use an opacimeter to carry out, and perhaps alternately can carry out through the size of direct measurement image element.Preferably, these pictorial elements are parts of a collimation template.In an especially preferred embodiment, these pictorial elements are track or point.

The size of measuring these tracks or point allows lens design to meet the actual characteristic of printing, and these characteristics depend on the kind and the employed pre-press equipment of printing equipment, printing ink and other materials.

Scale parameter can be estimated through mean value or the maximal value of calculating these pictorial element sizes.Alternately, it can use a kind of estimated value of robust to estimate, preferably one of mean value between median, upper quartile or the quartile of M-estimated value or pictorial element size.

Of the present invention one further aspect in, at this a kind of method of making optically variable device is provided, this method may further comprise the steps:

A substrate is provided;

A plurality of pictorial elements are applied on this substrate, and said pictorial element is to be arranged in an objective plane;

Confirm a scale parameter, this parameter is represented the size of these pictorial elements; And

In this on-chip a kind of transparent or semitransparent material, form a plurality of lenslets;

Wherein, Each lenslet has one group of lens parameter; This group parameter is confirmed as and makes these lenslets in this objective plane, have a focal spot size, and this focal spot size equates basically with the size of these pictorial elements in this objective plane or differs a predetermined value with the size of these pictorial elements.

In a preferred embodiment, this scale parameter is definite through the size of measuring these pictorial elements.

Preferably, this substrate is to form from a kind of transparent or semitransparent sheeting, wherein is formed with a plurality of lenslets on the first surface on the side of this substrate, and these pictorial elements are applied on the second surface on the opposition side of this substrate.These lenslets can be at this transparent or semitransparent sheeting from forming on one's body.Alternately, these lenslets can form in a transparent or semitransparent layer, for example carry out embossing through the transparent or semitransparent resin to a kind of radiation-hardenable, and it can be on transparent, the translucent or opaque substrate that this layer is applied to.

These pictorial elements can be formed by any technology easily, comprise printing or laser labelling.In an especially preferred embodiment, these pictorial elements are printing points.

In another aspect of the present invention; At this a kind of device of optically-variable is provided; This device comprise a substrate be formed among this substrate or on a plurality of lenslets and be positioned among the objective plane of this substrate or on a plurality of pictorial elements; Wherein each lenslet has one group of lens parameter; This group parameter is confirmed as and makes these lenslets in this objective plane, have a focal spot size, and this focal spot size equates basically with the size of these pictorial elements or differs a predetermined value with the size of these pictorial elements.

Preferably, these lenslets are the parts with lens arra of gauge thickness, and this gauge thickness is less than the focal length of each lenslet.

In one aspect of the method, the invention provides a kind of device of optically-variable, this device comprises a lens arra according to a first aspect of the invention.

Optically variable device by the said method manufacturing can be applied to large-scale object; Although the present invention is applied to the secure file field especially; And more specifically be to be applied to the secure file and the object that form by substrate flexibility, similar thin slice, like bank note or the like.This optically variable device can be formed in the window or half window zone of secure file.

Description of drawings

Now will only with reference to accompanying drawing the preferred embodiments of the invention be described with non-limiting mode of giving an example, in the accompanying drawings:

Fig. 1 shows a cross section passing lens arra in the prior art design;

Fig. 2 shows an embodiment of lens arra of the present invention;

Fig. 3 shows an alternate embodiment of lens arra of the present invention;

Fig. 4 to Fig. 6 described according to three lenslets of different embodiments of the present invention axle and from the axle focal spot size;

Fig. 7 shows the input and output point shape of two kinds of different printing technologies;

Fig. 8 shows the lenslet of prior art respectively and according to the power density distribution of the lenslet of one embodiment of the invention;

Fig. 9 shows the incident ray that lenslet is according to an embodiment of the invention passed through in refraction;

Figure 10 has described the geometry of a lenslet;

Figure 11 (a) has showed schematic sectional view of passing an object that is combined with a lens arra and a plurality of pictorial elements and a plurality of intermediate steps that form this object to Figure 11 (d);

Figure 12 (a) shows to Figure 12 (c) and passes a schematic sectional view that is similar to the object of Figure 11 (d), and this object is processed by a kind of method of revising;

Figure 13 (a) has showed schematic sectional view of passing a substituting object that is combined with a lens arra and a plurality of pictorial elements and a plurality of intermediate steps that form this object to Figure 13 (d);

Figure 14 and Figure 15 are block diagrams, show two different embodiments of a kind of lens arra manufacturing approach of the object that is used to produce Figure 11 to Figure 13;

Figure 16 is one group of printed image elements that interweaves of a lens devices instance; And

Figure 17 has showed when being in lobe subtended angle edge or a near angle at axle (a) with from axle (b) (simulation) relative brightness along these points of the width of the pictorial element of the device of Figure 16 when watching.

Embodiment

At first referring to Fig. 1; Showed a lens arra 20 of prior art design at this; It has a gauge thickness t, wherein have width W and basically the lenslet 22 of spheric profile incident ray 28a and 28b are focused on stain 26a and the white point 26b accordingly.These points have been printed on the lower surface 24.Thickness t is substantially equal to the focal length of these lenslets, so and focal spot size 30 be minimum value.

The focal spot size 30 of the lenslet of prior art is less than the printed resolution at lower surface 24 places.For example, conventional lens biasing lithography prints out about 25 microns average half tone dot size.Suitably design, width is that 254 microns lenses will be optical alignment to the axis on the about five microns focal spot size, this is basically less than the size of printing points 26a, 26b.

Referring now to Fig. 2,, shows a lens arra 120 according to a preferred embodiment of the invention at this.Incident ray 128a, 128b are accordingly towards a 26a, 26b and reflect.Lens arra 120 has thickness t ', this thickness is less than t, and these lenslets 122 have width W.Lenslet 122 is designed to make focal spot size 130a, 130b to be substantially equal to a 26a, 26b as follows.We have found that as long as focal spot size exceeds more than 20% unlike the mean breadth of printed half tone dot, the quality of image just can not be impaired.We have been found that also producing a kind of random, non-focusing design simply seriously degenerates picture quality, and this causes offensive fuzzy image.Focal spot size also can be slightly less than this mean breadth, preferably less than degree be no more than 20%.

Fig. 3 has described the design of a kind of substituting lens arra, lens arra 220 thickness t identical wherein with being in of prior art lens arra 20, but the width W of these lenslets 222 increases.Meanwhile, the other lenses parameter changes, and makes incident ray 228a, 228b reflected and arrive objective plane 224 like this so that intersect with a 26a, 26b, and focal spot size 230a, 230b equal a 26a, 26b once more basically on scope like this.For example, can make the radius-of-curvature of lens become big, as shown in Fig. 3, possible is lens parameter such as refractive index, circular cone parameter or the Abbe number that side by side changes other, so that obtain the optimal image quality.

Fig. 4 has showed the side cross-sectional view of the ray trajectory of a kind of wide-angle lenslet 105 that designs according to one embodiment of the invention.Many light 102 in the refraction of surperficial 101 places arrive objective plane 104 and have produced focal spot size 103A, 103B.In this embodiment, on the whole visual angle (this angle also be called as lobe subtended angle) of focal spot size of axle point 103A and off axis point 103B at lenslet by weighting comparably.

Fig. 5 has showed a kind of side cross-sectional view of ray trajectory of substituting wide-angle lenslet 101, and wherein in the lobe subtended angle, Focus width is substantially equal to the mean breadth of printed these half tone dots 109A.The side cross-sectional view of the ray trajectory of another wide-angle lenslet has been shown among Fig. 6, and wherein printed half tone dot 109A is still bigger, thus allow material thickness further to reduce or allows the lens frequency more roughly or both develop simultaneously.

In Fig. 7, top row 110 representatives of point are in a kind of a plurality of digital pixel 109B in the collimation format, that width is known that print, and they are outputed on the printed panel.Row 111 has been showed the print result of print line 110, and the gain of wherein significant point produces equalization point width 109C.Row 112 has showed that print line 110 uses the print result of another kind of printing processes, wherein its some gain even greater than the some gain of row 111, thus produce equalization point width 109D.In this diagram, can to the printing points in the row 111 use with row 112 in the different lens design of printing points, what the lens design of wherein optimizing for row 111 can be with Fig. 5 is similar, and is more similar that the lens design of row 112 optimizations can be with Fig. 6.

Referring now to Fig. 8,, shows the projection view of a printing half tone dot 109C who forms images by lenslet according to one embodiment of the invention at this.Fig. 8 (a) shows the profile 250 of power density distribution 255, if objective plane is positioned at 252 places, focal plane of array, this can cause and produce hot spot 256 (Fig. 9).In contrast, the hot spot 266 in the objective plane 262 is greater than a 109C, but has power density distribution 260,265, make so most of incident light still point of arrival 109C so that keep the sampling effect.

For a continuous tone images is printed onto on paper or the synthetic material (like plastics), need convert thereof into a half tone image.Known several different methods is used to change in this area.These class methods represent continuous tone through binary point (so-called amplitude modulation (AM) method) that uses different size or the point (so-called frequency modulation (FM) method) with same size and different frequency.Can also use the various combination (being called mixing method) of these two kinds of methods.For the purposes of the present invention, can use any in these methods.Yet, the FM method (in it is multi-form, include but not limited to: shake, error diffusion, or arbitrarily or shielding at random) be preferable methods because these points totally remain unchanged dimensionally.

The pattern measurement of printed half tone dot can use multiple known method to accomplish.For example; Can confirm the equalization point size through printing a compacting collimation template; This template is made up of the sample of a plurality of points of intended size and is had different density, and wherein each sample is typically represented from one of percentage to percent a ninety-nine density value.Subsequently this template is imaged onto on film or the plate, and it is printed onto on the smooth of an optical effect substrate.Then, scan print result with an opacimeter or similar instrument, so that confirm the size of printing points.

Alternately, can directly measure the equalization point size, for example use to be equipped with a microscope that shows the cross curve plate of measured value increment.In direct method, can in each tone value scope, measure, write down a sample of these points, and their size is averaged.

We have found that the measured value of these points provides optimum at about 20% tone value place.

In some instance, because pressing conditions that changes or the like, obtaining above-mentioned measured value perhaps is impossible or infeasible.If this situation, so can be or otherwise estimate an average expectation spot size from previous experience.

Referring to Figure 10, we describe a kind of method that the design of lenslet used in this invention is optimized now.From the purpose of this non-limiting example, we are chosen for rotational symmetric, aspheric lens with lenslet 300.This method depends on uses Theoretical Calculation that geometrical optics is carried out, simple relatively, and has ignored the edge effect of lens perimeter.The technician will recognize that many other methods are possible, comprise the more complicated physical model of use, ray tracing simulation or the like.

In Figure 10 (a); Being in a pictorial element with printing points 305 forms of overall with H and half-breadth h is positioned at from (x; Y) in the objective plane of unknown distance t of coordinate origin (gauge thickness), this pictorial element is corresponding to the peak 310 of lens 300.Lens 300 have sag height s and half-breadth w and refractive index n (not shown).Thereby a kind of lens design of optimization will make the incident ray 320 that is parallel to the incident of x axle reflect in the arrival of 315 places, edge of lens 300 and at an angle beta place and the roof intersection of point 305.Therefore we hope to find an expression formula to the t of lens parameter and half-breadth h, and half-breadth h is a scale parameter of representative point 305 sizes.

The equation of lens characteristics function y (x) is provided by following formula

P*x ²-2*R*x+y(x) ²＝0

Wherein R is the lens radius at rims of the lens 305 places, and P is the constant of the cone and equals 1-e ², wherein e is an excentricity.In principle, can select to comprise more high order lens characteristics function power, the more general y (x) of x.Yet,, be to use the quadratic form of aforesaid y (x) generally more easily from the purpose of lens design.

(x=s y=w) has a slope to the normal 330 of lens surface at 305 places on the edge of

$m\left(x\right)=\frac{-1}{y^{\′}\left(x\right)}$

Wherein y ' is the first order derivative of y (x) (x).This slope equals Tan (α), and wherein α is the angle between incident ray 320 and the normal 330, so and

Tan(α)＝m(x)

So

$\mathrm{\α}\left(x\right)=\mathrm{ArcTan}\left(\frac{\sqrt{2*R*x-P*x^2}}{P*x-R}\right).$

According to snell law,

n ₁*Sin(α)＝n*Sin(θ)

Wherein θ is the angle between refracted ray 320 ' and the normal 330, and n ₁It is the refractive index (after this being taken as 1 approx) of air.Therefore

$\mathrm{\θ}=\mathrm{ArcSin}\left(\frac{\mathrm{Sin}\left(\mathrm{\α}\right)}{n}\right).$

(s is w) with (t, the slope A of straight line h) is in connection

A＝-Tan(β)

And with β=α-θ substitution,

$A=-\mathrm{Tan}[\mathrm{\α}\left(s\right)-\mathrm{ArcSin}\left(\frac{\mathrm{Sin}\left(\mathrm{\α}\left(s\right)\right)}{n}\right)].---\left(1\right)$

This more directly expresses t and can be write and do

$t=s+\frac{h-w}{A}---\left(2\right)$

Wherein identical among A and the above-mentioned Eq (1), and

$\mathrm{\α}\left(s\right)=\mathrm{ArcTan}\left(\frac{w}{\sqrt{R^2-P*w^2}}\right).---\left(3\right)$

Can be directed against one or more among lens parameter R, n, P, w and the s and optimize thickness t, promptly equal zero through being made as to the partial derivative of expression formula among the one or more Eq of asking (2) in these parameters and with these partial derivatives with mode commonly used.Can analysis mode ground or numerical value formula ground the system of equations that is obtained is found the solution so that find the lens parameter group that provides optimum lens thickness.

This optimization can be constrained optimization.Therefore for example, on the scope of t, have the restriction of actual manufacturing, and what possibly hope is that t is limited in the scope of these values.The constrained optimization method is well known in the art.

Above-mentioned equality is that the incident ray that is parallel to the x axle is drawn.Can this derivation vague generalization be used for obtaining thus from axial ray 340,350 and a plurality of off axis point (Figure 10 (b))

D＝||(M-m)*(t-s)+2*w||，

Wherein D is the size of off axis point; M is the slope of the light 340 ' of refraction at 345 places, an edge of lenslet; And m is the slope of refracted ray 350 ' at opposite edge 355 places of lenslet, and t is desirable gauge thickness, and s is that sag height and w are the lens half-breadths as previously mentioned.

When the angle of deviation δ of incident ray is zero, M=-m=A, and equation simplify into

D＝2M*(t-s)+2w。

In this case, D becomes and equals full spot size 2h, and

$t=s+\frac{h-w}{A},$

This is corresponding to the expression formula of the on-axis light line that had before drawn.

As the replacement scheme of above-mentioned situation, might lens half-breadth w be optimized as some or whole functions among R, n, P and the s, t can remain unchanged simultaneously.This can accomplish through rewriteeing Eq (2) by following equality to w:

w＝h-A*(t-s)。

If t remains unchanged, can carry out constrained optimization and find optimum lens half-breadth w.

As another replacement scheme, can be with optimizing other lenses parameters R, n, P or s with the similar mode of above-mentioned situation.

Above-mentioned model also comprises the processing to aberration ambiguously.The technician will recognize that constant of the cone P and/or the Abbe number that can select lens minimize aberration.

An object 400 has been shown in Figure 11 (d), and this object is formed by a kind of substrate 410 of transparent or semitransparent material and has a lens arra 420 that on a front surface 411 of a side of substrate 410, forms and a plurality of pictorial element 426a, a 426b that on surface 412 behind on the opposition side of substrate 410, forms.In making a kind of method for optimizing of object 400, pictorial element 426a, 426b be at first be applied on the said opposition side, substrate 410 back surperficial 412 on (Figure 11 (a)). Pictorial element 426a, 426b preferably apply on the said back surface 412 through being printed on, though they can through additive method (comprising laser labelling) be formed within the said back surface or on.

Figure 11 (b) shows on the front surface 411 that a transparent or semitransparent embossable layer 415 is applied to transparent or semitransparent substrate 401.Preferably, this embossable layer is a kind of liquid, resin or printing ink of radiation-hardenable, and it can apply through a kind of typography.Then, with a kind of embossing pad 416 (Figure 11 (c)) come to layer 415 carry out embossing in case the lens arra 420 in the cambium layer 415, with substrate 410 back surperficial 412 on pictorial element 426a, 426b accurate and a plurality of lenslets 422.Embossed layer 415 can be solidified through radiation, and for example through UV, X ray, electron beam or heat (IR), this curing is perhaps carried out simultaneously in the embossing process or carried out thereafter, so that the boss structure of these lenslets 422 in the fixed lens array 420.

Referring to Figure 12; Show a kind of alternative method that is used to produce object 500 at this, the similar part of the object among this object and Figure 11 (d) is: it be substrate 510 by a kind of transparent or semitransparent material form and have lens arra 520 forming in the embossable layer 515 on being applied to a front surface 511 of substrate and substrate back surperficial 512 within or on a plurality of pictorial element 526a, the 526b that form.

In method shown in Figure 12; Embossable layer 515 at first is applied on the front surface 511 on the side of substrate 510 (Figure 12 (a)); And then,, pictorial element 526a, 526b come embossing (Figure 12 (b)) before being applied on back surperficial 512 on the opposition side of substrate 510 through embossing pad 516.Again; This embossable layer 515 is that liquid, resin or the printing ink by a kind of radiation-hardenable forms; It can preferably be able to apply through a kind of typography, and preferably or in the embossing process is side by side perhaps solidifying through radiation thereafter. Pictorial element 526a, 526b be through substrate 510 back surperficial 512 on print or laser labelling forms so that form object 500 that generated, Figure 12 (c).

In object 400,500 that generated, Figure 11 (d) and Figure 12 (c); What will be appreciated that is; Lens arra 420,520 has gauge thickness t=p+q; Wherein p is the thickness of this transparent or semitransparent substrate 410,510, and q is thickness that the summit from the front surface 411,511 of substrate 410,510 to each lenslet 422,522 is measured after embossing, this transparent or semitransparent layer 415,515.

In many cases; Substrate 410 will be predetermined with the thickness p and the q of layer 415; Equalization point size H=2h is confirmed by printing process or other technologies of being used to form these pictorial elements; And one or more lens parameters (for example lens width W=2w, radius of curvature R, sag height s, refractive index n or constant of the cone P) can about t (=p+q) be optimized, so that be used to form the embossing pad of lens arra 420,520 according to the method manufacturing of Figure 14 of explanation after a while.

Referring to Figure 13 (a) to Figure 13 (d); Show a kind of method that is used to produce object 600 at this, this object has a lens arra 620 that forms in the transparent or semitransparent layer 615 on pictorial element 626a on being applied to a front surface 611 of substrate 610 1 sides, the 626b.Substrate 610 among Figure 13 can be transparent, translucent or opaque, because lens arra 620 forms on the same side of substrate 610 with pictorial element 626a, 626b.In method shown in Figure 13, before applying transparent or semitransparent layer 615 (Figure 13 (b)) and coming embossing, pictorial element 626a, 626b at first are applied on the front surface 611 of substrate, preferably through printing (Figure 13 (a)) through embossing pad 616.Again; This embossable layer 615 can be that liquid, resin or the printing ink by a kind of radiation-hardenable forms; It can be able to apply through a kind of typography; And preferably or in the embossing process side by side perhaps solidifying through radiation thereafter, so that the lens arrangement of these lenslets 622 of fixed lens array 620.

Object 600 that obtained, Figure 13 (d) is with the difference of the object of Figure 11 (d) and Figure 12 (c); The thickness p of substrate 610 is to the not influence of gauge thickness t of lens arra 620, and this gauge thickness is (the allowing the thickness of pictorial element 626a, 626b) that equates with the thickness q of transparent or semitransparent layer 615 basically.Because the gauge thickness of the lens arra 620 of object 600 maybe be less than the gauge thickness t of the lens arra 420,520 of the object 400,500 of Figure 11 (a) and Figure 12 (a); So through suitably changing the shape of embossing pad 616, other parameters of the lenslet 622 that method of the present invention can be through reducing lens width W or radius of curvature R or adjustment lens arra 620 be used for to gauge thickness reduce compensate.

Referring now to Figure 14,, shows the process flow diagram of a kind of method that is used to make the embossing pad that uses with certain embodiments of the present invention at this.At first, a printing collimation template (step 700), and measurement point size (step 710) as stated.Then, select one group of initial lens parameter (step 720) and in a multivariate optimizing process (step 730,740), change these parameters.In case found one to separate, just can make an embossing pad (step 750) that is used for production run.

In Figure 15 (a) and Figure 15 (b), show two kinds of alternative method that are used to form the optical effect object.Under both of these case, a substrate (step 800) is provided at this.Process shown in Figure 15 (a) is suitable for forming the object 400 and 600 of Figure 11 and Figure 13.In the embodiment of Figure 15 (a), (step 810) gone up on the front surface or the surface, back that two or more images that interweave are applied to substrate, preferably through printing.Can a kind of printing ink of radiation-hardenable be applied to subsequently on the front surface of substrate (step 820),, and use a kind of embossing pad that obtains from the step 750 of Figure 14 that printing ink is carried out embossing then for example through a kind of typography.Then with the lenslet of ink solidification with the optical effect object in the formation embossed surfaces.(step 830) can take place with the embossing step in curing schedule basically simultaneously.In Figure 15 (b), the substitute is a side (step 840) that at first printing ink of radiation-hardenable is applied to substrate.Then, the embossing pad that obtains with the step 750 of Figure 14 carries out embossing to printing ink and solidifies to form these lenslets (step 850).Then pictorial element is applied on the substrate side opposite with these lenslets, with these lenslets accurate with so that form the optical effect object.

Instance

Referring to Figure 16, show an instance of printed interlaced image 900 at this, this image is used to when matching with a suitable lens arra, produce " stirring image " effect of a kind of binary.In shown instance, pictorial element is the black image element of the form that is in striped 901 that interweaves with the white image element that is in striped 902 forms.In this case, blackstreak is to be formed by the black ink that is printed on a hyaline layer or the white ink layer, makes white stripes formed by the white ink that the clear area that does not have printing ink does not perhaps apply black ink like this.When the lens array of the lens through having a plurality of microtrabeculae lens 930 is watched; Along with a kind of device of the combination with lens arra and pictorial element 901,902 is parallel to the axis of stripe direction with respect to the beholder about one and tilts; This device has produced from the switching of the image 910 of Figure 16 shown in upper left to image 920, and wherein the zone of black and white is put upside down.

Be applied on the substrate through the striped 901,902 of intaglio printing black and white.When using microscopical cross curve plate to measure, find that blackstreak has 32 microns mean breadth, and white stripes has 31.5 microns mean breadth.32 microns mean value of blackstreak is got the scale parameter of making the representative image element size.The width W (be shown in and overlap on the profile on the printed pictorial element 901,902) of microtrabeculae lens 930 is fixed on 63.5 microns, and uses the expression formula in the equation (2) that the gauge thickness t is optimized.This cause sag height s be 10 microns and radius of curvature R when being 55.4 microns optimum gauge thickness t be 90 microns, by contrast, if pictorial element is positioned at the empty focal length place of microtrabeculae lens then gauge thickness is about 162 microns.

For the focal spot size of checking microtrabeculae lens with above design whether enough near the size of pictorial element so that produce the desirable image effect that stirs, with above parameter be input to by Zemax Development Corporation produce and optical tracking simulation in the design of Optical System software that trade mark ZEMAX sells under one's name in.Can be used for confirming focal spot size at the relative brightness figure shown in Figure 17 (a) and Figure 17 (b), it is that relative brightness drops to these zero points accordingly to the distance between (960a, 960b) and (961a, 961b).Can see, in the edge of lobe subtended angle, be about 30 microns in the focal spot size 951 of axle, and be about 23 microns from the focal spot size 952 of axle.Therefore, a kind of " average " pictorial element of seeing on the axis will be focal spot size 6% to 7% within.

Will be appreciated that, under the situation that does not deviate from the spirit and scope of the present invention, can carry out various modifications embodiment of the present invention.For example, possiblely be, the lenslet structure of a lens arra can be direct embossing in a kind of surface of transparent or semitransparent substrate, rather than embossing is to being applied in the on-chip transparent or semitransparent embossable layer.And although printing is the selection process that is used to form these pictorial elements, these pictorial elements also can be formed by laser labelling.In this case; Might guide beam of laser directly to pass transparent or semitransparent substrate or layer and arrive on the side of substrate or layer from lasing light emitter; So that in one of the opposition side marked of substrate or layer to laser sensitive surface, thereby after lens arra forms, form these pictorial elements.

Claims (41)

1. one kind is used at the lens arra of objective plane with a plurality of pictorial element imagings; This lens arra comprise the side that is formed on a kind of transparent or semitransparent material among or on a plurality of lenslets; And these pictorial elements are placed on the opposition side; This lens arra have with from the summit of each lenslet to the corresponding gauge thickness of the distance of this objective plane; Wherein each lenslet has one group of lens parameter; This gauge thickness and/or at least one lens parameter are optimised for and make each lenslet in this objective plane, have a focal spot size, and this focal spot size equates basically with the size of these pictorial elements in this objective plane or differs a predetermined value with the size of these pictorial elements.

2. a manufacturing is used in the method for objective plane with the lens arra of a plurality of pictorial element imagings; This lens arra comprises a plurality of lenslets; This lens arra have with from the summit of each lenslet to the corresponding gauge thickness of the distance of this objective plane, this method may further comprise the steps:

Confirm a scale parameter, the size of this scale parameter representative these pictorial elements at least a portion of this objective plane,

Use this scale parameter to optimize at least one parameter in this gauge thickness and/or the one group of lens parameter for each lenslet,

And with said gauge thickness and said lens parameter among a kind of side of transparent or semitransparent material or on form this lens arra, and make these pictorial elements be placed in the opposition side of this transparent or semitransparent material,

Thus, make these lenslets in this objective plane, have a focal spot size, this focal spot size equates basically with the size of these pictorial elements or differs a predetermined value with the size of these pictorial elements.

3. according to claim 1 or described lens arra of claim 2 or method, wherein the lens parameter group of these lenslets comprises following two or more multinomial: lens width, refractive index, sag height, radius-of-curvature, circular cone parameter and Abbe number.

4. according to each described lens arra or method in the claim 1 to 3, wherein the gauge thickness of this lens arra is that size and this lens parameter group with respect to these pictorial elements is optimized.

5. according to each described lens arra or method in the claim 1 to 3, wherein these lens parameters are that size with respect to these pictorial elements is optimized with this gauge thickness.

6. according to claim 4 or described lens arra of claim 5 or method, wherein the gauge thickness of this lens arra is less than the focal length of all these lenslets.

7. according to each described lens arra or method in the above claim, wherein the predetermined value that differs of this focal spot size is the difference value less than an estimation of these pictorial element sizes.

8. lens arra according to claim 7 or method, wherein the difference value of this estimation is standard deviation, meta absolute deviation or the interquartile range of these pictorial element sizes.

9. according to each described lens arra or method in the above claim, wherein the predetermined value that differs of the size of this focal spot size and these pictorial elements is to be not more than 20% of these pictorial element sizes.

10. according to each described lens arra or method in the above claim, wherein these pictorial elements have been taked the form of a plurality of points or many lines.

11. according to each described lens arra or method in the above claim, wherein these pictorial elements are to be applied on the surface on the opposition side of this transparent or semitransparent material through printing.

12. according to each described lens arra or method in the above claim, wherein these pictorial elements are to be applied on the surface on the opposition side of this transparent or semitransparent material through laser labelling.

13. according to each described lens arra or method in the above claim; Wherein this lens arra comprises a substrate of transparent or semitransparent polymeric material; This substrate has one first or front surface and one second or surface, back; These lenslets be formed on this first or front surface on or among, and these pictorial elements be applied to this second or the back surface on.

14., wherein a plurality of printing points are printed in this objective plane on second or the surface, back of this substrate according to described lens arra of the claim 13 that is attached to claim 11 or method.

15. lens arra according to claim 11 or method wherein are printed on a plurality of printing points on the substrate, and this substrate is attached on a kind of transparent or semitransparent material of this lens arra.

16. according to each described lens arra or method in the above claim, wherein these lenslets are to be formed in a kind of material of transparent or semitransparent radiation-hardenable through a kind of embossing technique.

17. lens arra according to claim 16 or method; Wherein the material with this radiation-hardenable is applied on the substrate that is formed by a kind of transparent or semitransparent material, and the combination thickness of this substrate and radiation curable material is corresponding with the gauge thickness of this lens arra.

18. lens arra according to claim 17 or method, wherein this substrate and these lenslets have substantially the same refractive index.

19. according to each described lens arra or method in the above claim, wherein this lens parameter group is identical to each lenslet.

20. according to each described lens arra or method in the above claim, wherein these lenslets in one or more zones of this lens arra have the different lens parameter of these lenslets in another or a plurality of zone with this lens arra.

21. according to each described lens arra or method in the above claim; Wherein when after averaging on two or more directions within the lobe subtended angle of this lenslet, this focal spot size is to equal the size of these pictorial elements basically or differ a predetermined value with the size of these pictorial elements.

22. according to each described lens arra or method in the above claim, wherein the cross section that has of each lenslet is a conic section.

23. according to each described lens arra or method in the above claim, wherein each lenslet is rotational symmetric in the plane of this lens arra.

24. according to each described lens arra or method in the above claim, wherein each lenslet is one and has basic cross section uniformly, long and narrow microtrabeculae lens along its length.

25. method that is designed for the lens arra that in objective plane, a plurality of pictorial elements is formed images; This lens arra comprise a plurality of lenslets and have and from the summit of each lenslet to the corresponding gauge thickness of the distance of this objective plane, this method may further comprise the steps:

Estimate a scale parameter, the size of this scale parameter representative these pictorial elements in this objective plane,

For each lenslet is selected one group of lens parameter, and

Use this scale parameter to design this lens arra so that optimize at least one lens parameter in the lens parameter group of this gauge thickness and/or each lenslet; Wherein each lenslet has a focal spot size in this objective plane, and this focal spot size equates basically with the size of these pictorial elements in this objective plane or differs a predetermined value with the size of these pictorial elements.

26. method according to claim 25, wherein this lens parameter group comprises: refractive index, sag height, lens width, radius-of-curvature, circular cone parameter and Abbe number.

27. according to claim 25 or the described method of claim 26; Further may further comprise the steps: at least a portion of this objective plane, measure the size of these pictorial elements, wherein this scale parameter is to estimate from the size of these measured pictorial elements.

28. method according to claim 27, wherein this measurement is to use an opacimeter to carry out.

29. method according to claim 27, wherein this measurement is to carry out through the size of direct these pictorial elements of measurement.

30. according to each described method in the claim 27 to 29, wherein these pictorial elements are parts of a collimation template.

31. according to each described method in the claim 27 to 29, wherein this scale parameter is to estimate through mean value or the maximal value of calculating these pictorial element sizes.

32. according to each described method in the claim 27 to 30, wherein this scale parameter is to use the estimated value of a robust to estimate.

33. method according to claim 32, wherein the estimated value of this robust is the M-estimated value.

34. method according to claim 32, wherein the estimated value of this robust is one of median, upper quartile or range interquartile mean value of these pictorial element sizes.

35. a method of making optically variable device, this method may further comprise the steps:

A substrate is provided;

A plurality of pictorial elements are applied on this substrate, and said pictorial element is positioned in the objective plane;

Confirm a scale parameter, this parameter is represented the size of these pictorial elements; And

In this on-chip a kind of transparent or semitransparent material, form a plurality of lenslets;

Wherein, Each lenslet has one group of lens parameter; This parameter group is confirmed as and makes these lenslets in this objective plane, have a focal spot size, and this focal spot size equates basically with the size of these pictorial elements in this objective plane or differs a predetermined value with the size of these pictorial elements.

36. method according to claim 34, wherein this scale parameter is to confirm through the size of direct these pictorial elements of measurement.

37. optically variable device; Comprise a substrate be formed among this substrate or on a plurality of lenslets and be arranged among this substrate or on a plurality of pictorial elements of an objective plane; Wherein each lenslet has one group of lens parameter; This parameter group is confirmed as the focal spot size that these lenslets are had in this objective plane, this focal spot size equates basically with the size of these pictorial elements or differs a predetermined value with the size of these pictorial elements.

38. according to each described method or device in the claim 35 to 37, wherein these lenslets are parts of a lens arra, this lens arra has a gauge thickness less than the focal length of each lenslet.

39. an optically variable device comprises according to each described lens arra in the claim 1 to 24.

40. a secure file comprises according to each described optically variable device in the claim 35 to 37.

41. according to the described secure file of claim 40, wherein this optically variable device is formed among the window or half window zone of this secure file.

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